The days of sweat-soaked tank tops are behind us. And, honestly? Good riddance. Fall’s brisk weather brings with it the promise of cozy knitwear, cashmere socks, and roaring fires—perhaps the only downside is that the grey skies exacerbate the our considerable vitamin D deficiency. An estimated 35% people who live in the United States have a below optimal level of vitamin D, so taking supplements is recommended.
“Vitamin D becomes rather crucial to optimising overall health and wellbeing in autumn and winter,” says Jessica Shand, naturopathic nutritionist and author of The Hormone Balance Handbook. “We simply do not get enough UVB exposure [in many places across the world] during these months to reliably make adequate vitamin D through the skin.” Low vitamin D is nothing to shrug off, either: Aside from being key to supporting the immune system, bones and muscle health, insufficient levels could contribute to low mood, according to a National Health Institute study.
While certainly not a cure-all, taking supplements could even help to stave off seasonal affective disorder (SAD) at this time of year. “Seasonal affective disorder, or SAD, is a form of depression caused by reduced light exposure,” Kaywaan Khan, MD previously explained to Vogue. “When there is less natural daylight, the body’s melatonin and serotonin levels change, which affects our mood, sleep, and energy levels.”
Clinical nutritionist Lucy Miller adds: “Advice from the NHS is that everyone should consider a 10 microgram (400 IU) daily supplement during fall and winter because of how little usable sunlight we get.” No prescription needed, then. But Miller and Shand both agree that some might consider taking it year-round, including those with darker skin tones (melanin reduces vitamin D synthesis), people who have reduced contact with sunlight, and women.
“From a women’s health perspective, vitamin D is much more than a bone nutrient,” explains Shand. “Vitamin D receptors are found in reproductive tissues, too, and vitamin D has been studied in relation to ovarian function, fertility, insulin sensitivity, and conditions such as PMOS [polyendocrine metabolic ovarian syndrome].” Shand notes that while that doesn’t make vitamin D some kind of magical, hormone balancing supplement, it does play an important role in creating a healthier hormonal and metabolic environment.
If you’re unsure where you stand, Miller recommends checking your levels with a doctor or with a private test from a provider like Function Health. But for those planning to introduce it for cooler months, the question is, when is best to start? “If you have had adequate sun exposure over the summer, then starting in September or October and taking it through early March covers the low-sunlight window,” Miller says. She recommends taking the supplement in its D3 form, along with K2 and magnesium glycinate in order to support absorption.
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